U.S. patent application number 10/051703 was filed with the patent office on 2003-07-24 for electrical connection system for two printed circuit boards mounted on opposite sides of a mid-plane printed circuit board at angles to each other.
Invention is credited to Volstorf, James R..
Application Number | 20030137817 10/051703 |
Document ID | / |
Family ID | 21972851 |
Filed Date | 2003-07-24 |
United States Patent
Application |
20030137817 |
Kind Code |
A1 |
Volstorf, James R. |
July 24, 2003 |
Electrical connection system for two printed circuit boards mounted
on opposite sides of a mid-plane printed circuit board at angles to
each other
Abstract
An electrical connection system for two printed circuit boards
mounted on opposite sides of a mid-plane printed circuit board at
angles to each other. The system includes two connector printed
circuit boards, each containing pairs of electrical connections.
The connector boards are mounted on opposite faces of a mid-plane
printed circuit board, which contains pairs of overlaying via holes
on each of its faces. The via holes are positioned according to one
of two schemes. In the first scheme, the via holes are positioned
along an axis perpendicular to an axis that bisects the angle of
misalignment of the connector boards, and the via holes are
equidistant from a point on the axis that bisects the angle of
misalignment of the connector boards. In the second scheme, the via
holes are positioned along an axis that bisects the angle of
misalignment of the connector boards, and the via holes are
equidistant from each of the electrical connections. The electrical
connections on each of the connector boards are connected through
electrical paths. Each electrical path consists of a top
electrically conductive surface mount pad connecting the electrical
connection on the top connector board to a via hole on the top face
of the mid-plane board, a mid-plane electrical trace through the
mid-plane board connecting a via hole on the top surface of the
mid-plane board to the via hole directly beneath it on the bottom
face of the mid-plane board, and a bottom electrically conductive
surface mount pad connecting the via hole on the bottom face of the
mid-plane board to the electrical connection on the bottom
connector board.
Inventors: |
Volstorf, James R.;
(Mechanicsburg, PA) |
Correspondence
Address: |
Woodcock Washburn LLP
46th Floor
One Liberty Place
Philadelphia
PA
19103
US
|
Family ID: |
21972851 |
Appl. No.: |
10/051703 |
Filed: |
January 18, 2002 |
Current U.S.
Class: |
361/803 ;
174/262; 361/792 |
Current CPC
Class: |
H05K 1/114 20130101;
H05K 2203/1572 20130101; H05K 1/14 20130101 |
Class at
Publication: |
361/803 ;
361/792; 174/262 |
International
Class: |
H05K 001/11; H05K
001/14 |
Claims
What is claimed:
1. A routing system for interconnecting two surface mounted printed
circuit boards comprising: a mid-plane printed circuit board
including a first face and a second face, said second face parallel
to said first face; a first printed circuit board surface mounted
on said first face of said mid-plane printed circuit board, said
first printed circuit board containing pairs of electrical
connections; a second printed circuit board surface mounted on said
second face of said mid-plane printed circuit board, said second
printed circuit board containing pairs of electrical connections,
said second printed circuit boards mounted at an angle to said
first printed circuit boards; a plurality of pairs of via holes on
said first and second faces of said mid-plane printed circuit board
positioned with respect to the angle of misalignment of said first
and second printed circuit boards, said pairs of via holes on said
first face of said mid-plane printed circuit board directly
overlaying said pairs of via holes on said second face of said
mid-plane printed circuit board; and an plurality of electrical
paths through said overlaying pairs of via holes connecting said
pairs of electrical connections on said first printed circuit board
to said electrical connections on said second printed circuit
board.
2. A system as in claim 1, wherein said pairs of via holes are
positioned such that: A. each via hole in each of said pairs of via
holes is fixed on an axis perpendicular to an axis that bisects the
angle of misalignment of said first and second printed circuit
boards; and B. both via holes in each of said pairs of via holes
are equidistant from a point on an axis that bisects the angle of
misalignment of said first and second printed circuit boards.
3. A system as in claim 1, wherein said pairs of via holes are
positioned such that: A. each via hole in each of said pairs of via
holes is fixed on an axis that bisects the angle of misalignment of
said first and second printed circuit boards; and B. The distance
between the first via hole in each of said pairs of via holes and
the first electrical connection in one of said pairs of electrical
connections is equal to the distance between the second via hole in
each of said pairs of via holes and the second electrical
connection in one of said pairs of electrical connections.
4. A system as in claim 1, wherein said electrical paths are
substantially equal in length.
5. A system as in claim 1, wherein said electrical paths consist
of: a first face electrically conductive surface mount pad mounted
on said first face of said mid-plane printed circuit board
connecting one of said electrical connections on said first printed
circuit board to one of said via holes on said first face of said
mid-plane printed circuit board; an electrically conductive trace
connecting each of said via holes on said second face of said
mid-plane printed circuit board with the directly overlaying via
hole on said first face of said mid-plane printed circuit board;
and a second face electrically conductive surface mount pads
mounted on said second face of said mid-plane printed circuit board
connecting one of said electrical connections on said second
printed circuit board to one of said via holes on said second face
of said mid-plane printed circuit board.
6. A system as in claim 5, wherein said electrically conductive
traces pass straight through said mid-plane printed circuit board
at an angle perpendicular to said mid-plane printed circuit
board.
7. A system as in claim 5, wherein said electrically conductive
traces are substantially equal in length.
8. A system as in claim 5, wherein said first face electrically
conductive surface mount pads are substantially equal in
length.
9. A system as in claim 5, wherein said second face electrically
conductive surface mount pads are substantially equal in
length.
10. A system as in claim 5, wherein said first face electrically
conductive surface mount pads are substantially equal in length to
said second face electrically conductive surface mount pads.
11. A system as in claim 5, wherein each of said first face surface
mount pads connecting the first electrical connection in each of
said pairs of electrical connections is a long surface mount pad
and each of said first face surface mount pads connecting the
second electrical connection in each of said pairs of electrical
connections is a short surface mount pad.
12. A system as in claim 11, wherein each of said long surface
mount pads is substantially equal in length.
13. A system as in claim 11, wherein each of said short surface
mount pads is substantially equal in length.
14. A system as in claim 5, wherein each of said second face
surface mount pads connecting the first electrical connection in
each of said pairs of electrical connections is a short surface
mount pad and each of said second face surface mount pads
connecting the second electrical connection in each of said pairs
of electrical connections is a long surface mount pad.
15. A system as in claim 14, wherein each of said long surface
mount pads is substantially equal in length.
16. A system as in claim 14, wherein each of said short surface
mount pads is substantially equal in length.
17. A system as in claim 1, wherein said first and second printed
circuit boards are orthogonal.
18. A system as in claim 1, wherein said first and second printed
circuit boards are five by eight headers.
19. A system for interconnecting two surface mounted printed
circuit boards comprising: a mid-plane printed circuit board
including a first face and a second face, said second face parallel
to said first face; a first printed circuit board surface mounted
on said first face of said mid-plane printed circuit board, said
first printed circuit board containing pairs of electrical
connections; a second printed circuit board surface mounted on said
second face of said mid-plane printed circuit board, said second
printed circuit board containing pairs of electrical connections,
said second printed circuit boards mounted at an angle to said
first printed circuit boards; a plurality of pairs of via holes on
said first and second faces of said mid-plane printed circuit board
positioned such that: A. Each via hole in each of said pairs of via
holes is fixed on an axis perpendicular to an axis that bisects the
angle of misalignment of said first and second printed circuit
boards; B. Both via holes in each of said pairs of via holes is
equidistant from a point on an axis that bisects the angle of
misalignment of said first and second printed circuit boards; and
C. Each of said pairs of via holes on said first face of said
mid-plane printed circuit board is directly overlaying one of said
pairs of via holes on said second face of said mid-plane printed
circuit board; a plurality of electrically conductive traces
connecting each of said via holes in said pairs of via hole on said
second face of said mid-plane printed circuit board one of said
directly overlaying via holes in said pairs of via holes on said
first face of said mid-plane printed circuit board, said
electrically conductive traces being substantially equal in length;
a plurality of long first face electrically conductive surface
mount pads mounted on said first face of said mid-plane printed
circuit board, said long first face electrically conductive surface
mount pads connecting the first connection in each of said pairs of
electrical connections on said first printed circuit board to the
first via hole in each of said pairs via holes on said first face
of said mid-plane printed circuit board, said long first face
electrically conductive surface mount pads being substantially
equal in length; a plurality of short first face electrically
conductive surface mount pads mounted on said first face of said
mid-plane printed circuit board, said short first face electrically
conductive surface mount pads connecting the second connection in
each of said pairs of electrical connections on said first printed
circuit board to the second via hole in each of said pairs via
holes on said first face of said mid-plane printed circuit board,
said short first face electrically conductive surface mount pads
being substantially equal in length; a plurality of short second
face electrically conductive surface mount pads mounted on said
second face of said mid-plane printed circuit board, said short
second face electrically conductive surface mount pads connecting
the first connection in each of said pairs of electrical
connections on said second printed circuit board to the first via
hole in each of said pairs via holes on said second face of said
mid-plane printed circuit board, said short second face
electrically conductive surface mount pads being substantially
equal in length; and a plurality of long second face electrically
conductive surface mount pads mounted on said second face of said
mid-plane printed circuit board, each of said long second face
electrically conductive surface mount pads connecting the second
connection in each of said pairs of electrical connections on said
second printed circuit board to the second via hole in each of said
pairs via holes on said second face of said mid-plane printed
circuit board, said long second face electrically conductive
surface mount pads being substantially equal in length.
20. A system for interconnecting two surface mounted printed
circuit boards comprising: a mid-plane printed circuit board
including a first face and a second face, said second face parallel
to said first face; a first printed circuit board surface mounted
on said first face of said mid-plane printed circuit board, said
first printed circuit board containing pairs of electrical
connections; a second printed circuit board surface mounted on said
second face of said mid-plane printed circuit board, said second
printed circuit board containing pairs of electrical connections,
said second printed circuit boards mounted at an angle to said
first printed circuit boards; a plurality of pairs of via holes on
said first and second faces of said mid-plane printed circuit board
positioned such that: A. each via hole in each of said second face
pairs of via holes is fixed on an axis that bisects the angle of
misalignment of said first and second printed circuit boards; B.
The distance between the first via hole in each of said second face
pairs of via holes and the first electrical connection in one of
said pairs of electrical connections on said second printed circuit
board is equal to the distance between the second via hole in each
of said second face pairs of via holes and the second electrical
connection in one of said pairs of electrical connections on said
second printed circuit board; and C. each of said pairs of via
holes on said first face of said mid-plane printed circuit board is
directly overlaying one of said pairs of via holes on said second
face of said mid-plane printed circuit board; a plurality of
electrically conductive traces connecting each of said via holes in
said pairs of via hole on said second face of said mid-plane
printed circuit board one of said directly overlaying via holes in
said pairs of via holes on said first face of said mid-plane
printed circuit board, said electrically conductive traces being
substantially equal in length; a plurality of first face
electrically conductive surface mount pads mounted on said first
face of said mid-plane printed circuit board, each of said first
face electrically conductive surface mount pads connecting one of
said electrical connections on said first printed circuit board to
one of said via holes on said first face of said mid-plane printed
circuit board, said first face electrically conductive traces being
substantially equal in length; and a plurality of second face
electrically conductive surface mount pads mounted on said second
face of said mid-plane printed circuit board, each of said second
face electrically conductive surface mount pads connecting one of
said electrical connections on said second printed circuit board to
one of said via holes on said second face of said mid-plane printed
circuit board, said second face electrically conductive traces
being substantially equal in length to said first face electrically
conductive traces.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to electrical connections of
two printed circuit boards surface mounted on opposite sides of a
mid-plane printed circuit board at angles to each other.
Specifically, the invention is a routing scheme providing a direct
electrical path between electrical connections.
[0003] 2. Description of the Prior Art
[0004] Modern electronic devices such as computers must be able to
perform complex functions both quickly and effectively. Thus, it is
essential that the internal hardware of these electrical devices is
connected in an efficient manner. A common hardware assembly
technique involves two printed circuit boards, commonly referred to
as daughter boards, that are connected to opposite sides of a
mid-plane printed circuit board, commonly referred to as a mother
board. These daughter boards are often connected at angles to each
other. For the electrical device to function as desired, the
electrical components on one daughter board must be able to
transmit and receive electrical signals to and from the electrical
components on the other daughter board.
[0005] There are several devices known in the prior art that
provide such an electrical connection between two daughter boards.
For example, Petit et al. describe in U.S. Pat. No. 4,703,394 a
system for interconnecting orthogonally disposed printed circuit
boards. This system involves the use of four multiway connectors.
Two of the connectors are mounted on respective facing edges of the
connector boards, and two of the connectors are mounted on opposite
sides of the mid-plane board. The connectors mounted on the
connector boards plug into the connectors mounted on the mid-plane
board.
[0006] The interconnection system described in the Petit et al.
requires the use of bulky connectors that makes its implementation
undesirable in modern electrical devices which require a compact
design.
[0007] Sample et al. describe in U.S. Pat. No. 5,887,158 a
switching mid-plane and interconnecting system for interconnecting
large numbers of signals. This system contains a mid-plane printed
circuit board having a plurality of first connectors oriented in a
first direction on one side of the mid-plane for making connections
to the plurality of first printed-circuit boards. The mid-plane
printed-circuit board also has a plurality of second connectors
oriented in a second direction orthogonal to the plurality of first
connectors on the other side of the mid-plane. The connectors are
positioned such that connection pins on the plurality of first
connectors and plurality of second connectors in regions of
intersection are double-ended pins common to both. The remaining
connection pins of the plurality of first connectors are
single-ended connection pins which are connected to the
single-ended connection pins of the plurality of second connectors
via conductive traces on the mid-plane printed-circuit board.
[0008] The interconnection system described in the Sample et al. is
subject to two important drawbacks relating to the connection of
the single ended connection pins. First, the electrical path
connecting the single ended connection pins may vary in length. If
the contacts are used for differential signals, this presents a
problem because a longer electrical path may result in signals
which are out of phase. Additionally, the electrical path
connecting the single ended pins may run through the mother board
diagonally rather than straight (at an angle perpendicular to the
top and bottom side of the mother board). This diagonal electrical
path presents a problem because it results in the entrance and exit
of the electrical path into and out of the mother board to be
misaligned, thereby creating the need for additional drilling in
the mother board and further raising the complexity of the
design.
[0009] Thus, there is a need for a connection system that provides
a routing scheme in which the electrical paths between connections
in each pair of connections are of equal length. Furthermore, there
is a need for a connection system that provides a routing scheme in
which the electrical path runs straight through the mother board so
that the entrance and exit of the electrical path into and out of
the mother board directly overlay one another. Additionally, it is
desired that this connection system is a compact system that does
not require the use of bulky connector plug-ins. A connection
system with these and other improve characteristics is desired.
SUMMARY OF THE INVENTION
[0010] The present invention is an electrical connection system
that includes two connector printed circuit boards surface mounted
on opposite sides of a mid-plane printed circuit board at angles to
each other. Each of the connector boards contains pairs of
electrical connections. An electrical path connects each electrical
connection on the first connector board to a corresponding
electrical connection on the second connector board. This
electrical path consists of three elements. The first element is
preferably an electrically conductive surface mount pad connecting
each electrical connection on the first connector board to a via
hole on the first face of the mid-plane board. The second element
is preferably a mid-plane electrical trace through two overlaying
via holes on each face of the mid-plane board. This connection is
straight through the mid-plane board at an angle perpendicular to
each face of the board. The third element is preferably another
electrically conductive surface mount pad connecting the via holes
on the second face of the mid-plane board to the corresponding
electrical connection on the second connector board.
[0011] The length of the mid-plane electrical trace is preferably
equal to the width of the mid-plane board. However, the length of
the surface mount pads may vary provided that the total length of
the electrical path connecting the first connections in each pair
of electrical connections is equal to the total length of the
electrical path connecting the second connections in the pair.
[0012] In a preferred embodiment, each via hole in each pair is
fixed on an axis perpendicular to an axis that bisects the angle of
misalignment of the connector boards. Additionally, each via hole
in each pair may be equidistant from a point on an axis that
bisects the angle of misalignment of the connector boards. For the
electrical paths connecting the first connections in each of the
pairs of electrical connections, the first element will be a long
surface mount pad and the third element will be a short surface
mount pad. Conversely, for the electrical paths connecting the
second connections in each of the pairs of electrical connections,
the first element will be a short surface mount pad and the third
element will be a long surface mount pad. Thus, the total length of
the electrical path connecting the first connections in each pair
of electrical connections is equal to the total length of the
electrical path connecting the second connections in the pair.
[0013] In a another preferred embodiment, each via hole in each
pair is fixed directly on an axis that bisects the angle of
misalignment of the connector boards. In this embodiment, all
surface mount pads are equal in length. Thus, the total length of
the electrical path connecting the first connections in each pair
of electrical connections is equal to the total length of the
electrical path connecting the second connections in the pair.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention will be better understood after
reading the following detailed description of the presently
preferred embodiments thereof with reference to the appended
drawings, in which:
[0015] FIG. 1 illustrates a diagram of a first embodiment of the
electrical connection system with the via holes fixed on an axis
perpendicular to an axis that bisects the angle of misalignment of
the connector boards.
[0016] FIG. 2 illustrates a diagram of the first embodiment adapted
to a solder on surface mount connector where the front and backside
daughter boards are orthogonal to each other.
[0017] FIG. 3 illustrates a diagram of the second embodiment of the
electrical connection system with the via holes fixed on an axis
that bisects the angle of misalignment of the connector boards.
[0018] FIG. 4 illustrates a diagram of the second embodiment
adapted to a solder on surface mount connector where the front and
backside daughter boards are orthogonal to each other.
[0019] FIG. 5 illustrates a top view of the top surface of a mother
board with two exemplary 5.times.8 headers on opposite sides of the
mother board.
[0020] FIG. 6 illustrates a top view of the bottom surface of a
mother board with two exemplary 5.times.8 headers on opposite sides
of the mother board.
[0021] FIG. 7 illustrates a top view of the top surface and bottom
surface of a mother board overlaid with two exemplary 5.times.8
headers on opposite sides of the mother board.
[0022] FIG. 8 illustrates a view of the interlayer routing between
unmatched pairs of connections of two exemplary 5.times.8 headers
on opposite sides of the mother board.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0023] A system which meets the above-mentioned objects and
provides other beneficial features in accordance with the presently
preferred exemplary embodiment of the invention will be described
below with reference to FIGS. 1-8. Those skilled in the art will
readily appreciate that the description given herein with respect
to those figures is for explanatory purposes only and is not
intended in any way to limit the scope of the invention. Throughout
the description, like reference numerals will refer to like
elements in the respective figures.
[0024] FIG. 1 illustrates a diagram of a first embodiment of the
electrical connection system with the via holes fixed on an axis
perpendicular to an axis that bisects the angle of misalignment of
the connector boards. Misalignment angle A represents the angle of
misalignment of top connector board 101 and bottom connector board
102. Bisecting axis 103 bisects angle A. Perpendicular axis 104
intersects bisecting axis 103 at intersection point P at an angle
perpendicular to bisecting axis 103. Top surface via holes 111a and
112a are fixed along perpendicular axis 104 and are equidistant
from intersection point P.
[0025] FIG. 2 illustrates a diagram of the first embodiment adapted
to a solder on surface mount connector where the front and backside
daughter boards are orthogonal (misalignment angle A=90 degrees).
The first column of FIG. 2 illustrates a top view of the top
surface of the PWB. Top surface mount pads 201a and 202a connect
top daughter board connections 211a and 212a to via holes 111 and
112. The second column of FIG. 2 illustrates a top view of the
bottom surface of the PWB. Bottom surface mount pads 201b and 202b
(shown by dashed lines) connect bottom daughter board connections
211b and 212b to via holes 111 and 112. The third column of FIG. 2
illustrates a top view of the top surface and bottom surface of the
PWB overlaid. Top first connection 211a is the outside connection
on the top connector board, and bottom first connection 211b is the
inside connection on the bottom connector board. Conversely, top
second connection 212a is the inside connection on the top
connector board, and bottom second connection 212b is the outside
connection on the bottom connector board. Thus, this scheme is
ideal for connecting boards oriented in directions such that the
electrical signals travel from outside connections to inside
connections.
[0026] The electrical path from the first top board connection 211a
to the first bottom board connection 211b includes long top surface
mount pad 201a and short bottom surface mount pad 201b. The
electrical path from second top board connection 202a to second
bottom board connection 202b includes short top surface mount pad
202a and long bottom surface mount pad 202b. As can be seen, both
electrical paths consist of one long surface mount pad and one
short surface mount pad. Both electrical paths are, therefore, of
equal length. This ensures that the electrical signals transferred
between electrical connections on each of the connector boards will
not be out of phase. As may also be seen, first top surface via
hole 111a directly overlays first bottom surface via hole 111b and
second top surface via hole 112a directly overlays second bottom
surface via hole 112b. Thus, the electrical connection between via
holes is straight through the mid-plane board at an angle
perpendicular to faces of the mid-plane board. This allows for a
straight through drilling procedure in construction of the
mid-plane board.
[0027] FIG. 3 illustrates a diagram of a second embodiment of the
electrical Connection system with the via holes fixed on an axis
that bisects the angle of misalignment of the connector boards.
Misalignment angle A represents the angle of misalignment of top
connector board 101 and bottom connector board 102. Bisecting axis
103 bisects angle A. Top surface via holes 111a and 112a are fixed
along bisecting axis 103.
[0028] FIG. 4 illustrates a diagram of a second embodiemnt adapted
to a solder on surface mount connector where the front and backside
daughter boards are orthogonal (misalignment angle A=90 degrees).
The first column of FIG. 4 illustrates a top view of the top
surface of the PWB. Top surface mount pads 201a and 202a connect
top daughter board connections 211a and 212a to via holes 111 and
112. The second column of FIG. 4 illustrates a top view of the
bottom surface of the PWB. Bottom surface mount pads 201b and 202b
(shown by dashed lines) connect bottom daughter board connections
211b and 212b to via holes 111 and 112. The third column of FIG. 4
illustrates a top view of the top surface and bottom surface of the
PWB overlaid. In this scheme, both first connections 211a,b are the
outside connections, and both second connections 212a,b are the
inside connections. Thus, this scheme is ideal for connecting
boards oriented in directions such that the electrical signals
travel from outside connections to outside connections and inside
connections to inside connections.
[0029] The electrical path from the first top board connection 211a
to the first bottom board connection 211b includes top surface
mount pad 201a and bottom surface mount pad 201b. The electrical
path from second top board connection 212a to second bottom board
connection 212b includes top surface mount pad 202a and bottom
surface mount pad 202b. In this scheme, the length of all surface
mount pads are equal because the distance from each via hole to
each electrical connector is equal. All electrical paths are,
therefore, of equal length.
[0030] FIGS. 5-8 illustrate how the first routing scheme discussed
generally in FIGS. 1 and 2 would be specifically implemented to the
connection of two exemplary 5.times.8 headers on opposite sides of
the mother board. This illustration is for exemplary purposes only
and is no way intended to limit the scope of this invention. FIG. 5
illustrates a top view of the top surface of a mother board with
two exemplary 5.times.8 headers on opposite sides of the mother
board. FIG. 6 illustrates a top view of the bottom surface of the
mother board. FIG. 7 illustrates a top view of the top surface and
bottom surface of the mother board overlaid. There is a total of 40
pairs of connections. However, as is apparent from an examination
of FIGS. 5-7, the routing scheme of this invention can only be
applied to 33 of the 40 total pairs. The pattern in this case is a
combination of two 4.times.4 patterns for a subtotal of 32 pairs.
The 33.sup.rd pair is the one of a kind pair in the top right
corner of the diagrams. The 7 remaining pairs of the top most row
and the right most column must be connected using the interlayer
routing scheme shown in FIG. 8. While the invention has been
described and illustrated with reference to specific embodiments,
those skilled in the art will recognize that modification and
variations may be made without departing from the principles of the
invention as described above and set forth in the following claims.
For example, while the invention has been described as being used
to connect orthogonal first and second printed circuit boards, the
invention may be used to connect printed circuit boards at any
angle of misalignment. Furthermore, first and second printed
circuit boards may contain any size pattern of connections and is
not intended to be limited to a five by eight pattern of
connections. Accordingly, reference should be made to the appended
claims as indicating the scope of the invention.
* * * * *